/Engine/Plugins/Runtime/XRBase/Source/XRBase/Public/XRRenderTargetManager.h
Return the current render bridge for use by the current viewport. Override this method if your device implements a customFXRRenderBridge. Should only return non-null if the render bridge is initialized and should be used for the current frame
virtual [FXRRenderBridge](API\Plugins\XRBase\FXRRenderBridge) * GetActiveRenderBridge_GameThread ( bool bUseSeparateRenderTarget )